1. Technical Field
The present disclosure relates to a light emitting diode (LED).
2. Description of the Related Art
LEDs are semiconductors that convert electrical energy into light. Compared to conventional light sources, the LEDs have higher energy conversion efficiency, higher radiance (i.e., they emit a larger quantity of light per unit area), longer lifetime, higher response speed, and better reliability. At the same time, LEDs generate less heat. Therefore, LED modules are widely used in particular as a semiconductor light source in conjunction with imaging optical systems, such as displays, projectors, and so on.
Referring to FIG. 6, a typical LED 10, according to the prior art includes a substrate 110, a GaN bumper layer 120, an N-type GaN layer 132, an active layer 134, a P-type GaN layer 136, and a transparent contact layer 140. The GaN bumper layer 120, the N-type GaN layer 132, the active layer 134, the P-type GaN layer 136, and the transparent contact layer 140 are stacked on the substrate 110. The LED 10 further includes a transparent conductive layer 150, a first electrode 142, and a second electrode 144. The first electrode 142 is disposed on the N-type semiconductor layer 132. The transparent conductive layer 150 and the second electrode 144 are disposed on the transparent contact layer 140. The transparent conductive layer 150 is made of indium tin oxide (ITO) and the ITO is sputtered on an area of the transparent contact layer 140. Due to the net structure of the ITO layer, the lateral distribution of current applied on the transparent conductive layer 150 is uniform, thereby improving the extraction efficiency of light of the LED. However, the ITO layer has some faults, such as low mechanical strength and resistance distribution. Furthermore, the transparency of the ITO layer may be decreased in humid environments and the ITO layer may absorb some of the light emitted by the active layer 134 when the ITO fully covers the P-type semiconductor layer 136.
What is needed, therefore, is a light emitting diode, which can overcome the above-described shortcomings.